Can you guess what does this picture represent?
Manufacturing of an electronic device typically requires numerous steps and components. Additionally, numerous chemicals are used in the processes. These are potential sources for impurities such as chemicals or particles. If impurities are left on components they can cause problems and poor quality in further processing steps or reliability problems later during use. Impurities can for example cause contamination, corrosion, delamination and short circuits and significantly affect the functionality of a device. Often cleaning of all impurities from a device is impractical or even impossible. Furthermore, the use conditions are often sources of impurities, causing similar problems.
The picture above is from a contaminated surface of a printed circuit board (PCB). Two weeks ago our picture of the week dealt with anisotropic conductive adhesives (ACA and ACF). This PCB is meant for an ACF attachment. Before cleaning it had considerable impurities due to other processing steps, as shown in the picture. In adhesive attachments cleanliness of the substrate or PCB is critical. The impurities can significantly reduce the adhesion strength of adhesive material. In ACAs this can lead to increased resistance values. However, quite often the interconnections seem fine just after the attachment process. The problems may arise later when the attachments are exposed to their use conditions, causing unexpected early failures. Sometimes all attachments fail due to contamination, which can cause considerable expenses. This makes cleanness a key factor for ACA process.